1. Field of the Invention
This invention relates to the monitoring of environmental pollution, and more specifically to an unmanned integrated RES for remotely monitoring the exhaust gas composition of moving motor vehicles.
2. Description of the Related Art
Environmental pollution is a serious problem which is especially acute in urban areas. A major cause of this pollution is exhaust emissions from automotive vehicles. Official standards have been set for regulating the allowable amounts of pollutants species in automobile exhausts, and in some areas, periodic inspections or “smog checks” are required to ensure that vehicles meet these standards.
Anti-pollution devices which are required equipment on newer vehicles accomplish their intended purpose of reducing pollution in the vehicle exhaust to within prescribed levels. However, some older vehicles and special types of vehicles are exempt from inspections. Furthermore, some vehicle owners with mechanical expertise can perform whatever servicing is necessary to place their vehicles in condition to pass required inspections, and subsequently remove anti-pollution devices and/or return the vehicles with an attendant increase in pollutant emissions for normal use. The relatively small number of noncomplying vehicles generate a disproportionately large amount of pollution.
As a result, an anti-pollution program which depends entirely on mandatory periodic inspections performed at fixed facilities is inadequate. It is necessary to identify vehicles which are actually operating in violation of prescribed emission standards, and either require them to be placed in conformance with the standards or be removed from operation.
Manned RESs are now used to augment the periodic inspection program to identify vehicles that are in violation of the emission standards. In general, RES are a nonobtrusive and cost-effective means for identifying the high pollution emitting vehicles and notifying the owner to take corrective action in a timely manner. The Smog Dog™ RES produced by Santa Barbara Research Center, the assignee of the present invention, includes a source and a receiver that are mounted on respective tripods and positioned on opposite sides of a road, a video camera and speed sensor that are mounted on a tripod that is positioned about 50 feet up the road in the direction of oncoming traffic, a van that contains a computer, data storage, power sources, calibration gas, and a video monitor, and a technician.
The source projects an IR beam across the road to the receiver which continuously senses pollutant levels such as carbon monoxide (CO), carbon dioxide (CO2), hydrocarbons (HC), water (H2O), nitric oxide (NOx) in the received IR beam. When a vehicle passes through the IR beam, a sensor triggers the receiver to write the pollutant levels for the vehicle's exhaust plume to a data file in the data storage. The beam is set at a height to detect either low profile vehicles (cars) or high profile vehicles (trucks), but not both. The video camera takes a picture of the passing vehicle and the computer executes a character recognition program to identify the plate, which is then appended to the data file. If the speed sensor determines that the vehicle's acceleration and/or speed exceed certain levels, indicating that the vehicle's emissions control equipment are disabled, the recorded data is invalidated.
One drawback of the SMOG Dog™ and the other known RES systems is that the components, i.e. the sensor, receiver, video camera/speed sensor, and the van, are discrete parts that are positioned over a relatively large area. The source and receiver are positioned on opposite sides of the road. For safety purposes, they must be set back from the edges of the road. The video camera/speed sensor are positioned up the road such that their detection angles with respect to the passing vehicles is sufficiently shallow, approximately 3 degrees, to provide an accurate acceleration estimate and a high confidence of plate recognition. This can cause mismatch errors between the emissions readings and the plate recognition. Also, there must be enough room to park the van. These spatial requirements limit the applicability of the known RES systems. Furthermore, the discrete components are expensive because they require their own tripod, power supply, and alignment mechanisms.
Another drawback is that the known RES must be continuously manned by a technician, which is very expensive. After initial set up and alignment, the technician monitors the equipment to protect it from vandalism, performs required maintenance, and puts the system away at the end of the day. For example, the components may fall out of alignment due to the vibrations caused by passing vehicles, the various lenses may become occluded or the calibration gas may run out. Furthermore, the technician controls the data gathering process. The technician periodically places the RES in calibration mode, puffs a calibration gas into the IR beam to calibrate the system and evaluates the results displayed on the video monitor to accept or reject the calibration. Thereafter, the technician places the RES in data gathering mode, puffs the calibration gas, and compares the computed pollutant levels to the known levels of the calibration gas to accept or reject the verification of the calibration. During data gathering, the technician monitors both the signal levels of the exhaust plumes and the ambient air to determine whether the system has gone out of calibration or has a mechanical error. The technician also verifies the results of the plate recognition system.
U.S. Pat. No. 5,418,366 “IR-Based Nitric Oxide Sensor Having Water Vapor Compensation” issued May 23, 1995 discloses a specific receiver configuration having three channels for measuring a NO transmission, a water transmission, and a reference transmission, respectively, that are combined to give the effective NO transmission value. U.S. Pat. No. 5,210,702, “Apparatus for Remote Analysis of Vehicle Emissions” issued May 11, 1993 discloses a specific receiver configuration in which the ultraviolet beam is separated from the IR beam to sense the NO levels, and the IR beam is split into a plurality of components to measure CO, CO2, HC and H2O. Both systems use discrete source and receiver components placed on opposite sides of a road, a camera mounted on a tripod up the road, and a van for housing the control electronics, and require a technician to set the system up, calibrate the system, control the data gathering process, and pack it up at the end of the day.
In 1992 Remote Sensing Technologies (RST) experimented with a double-pass RES system called the RSD1000 in which a van housing both the source and the receiver and the video camera was suspended from a 20 foot boom. The IR beam was reflected off a mirror on the opposite side of the road back to the receiver. RST's system did not include the plate recognition or speed sensing capabilities, and never worked well enough for commercial exploitation. As a result, RST developed a one-pass system with the source and receiver on opposite sides of the road.